Limits of expression with square root

[engineer23]

I am looking at the derivation for an expression that relates the concentration of an oxide to time. It appears that to do this, the author takes the limit of sqrt(A+Bt), where A and B are constants as t approaches zero and infinity. Is there an easy way to do this without making assumptions about the sizes of the terms (ex. Bt >> A)? Could I expand this as a Taylor series?

 

[mathman]

Since the sqrt is continuous, when t->0 you are simply left with sqrt(A). As t->oo, as long as B >0, eventually Bt >> A, so it behaves like sqrt(Bt).